In one aspect, this invention relates to a multipurpose apparatus having the capability to internally clean a hydraulic system. In another aspect, this invention relates to a method for internally cleaning a hydraulic system.
As oil and gas production has moved into deeper water with production equipment placed on the seabed floor, it has become necessary to use remotely operated well control devices. These control devices are controlled from the surface via a hydraulic control system having numerous components and are typically located on the subsea wellhead tree.
It is very important that everything in the system be extremely reliable. The inability to actuate a controller on the seabed floor can result in lost production, which, because of the inaccessibility of the controller, may continue for many days, resulting in large losses of earnings and high costs of repairs. Reliable controller performance is also important for safety functions, and to protect the environment. In extreme cases, the failure of a controller to perform can have catastrophic consequences.
Contaminated hydraulic fluid can lead to failures in hydraulic components and controls. Particulate contamination, for example, in the hydraulic fluid can, over time, damage the seals in the controllers, which are typically valves with hydraulic actuators. Cleaning the hydraulic system reduces this risk and therefore has become a standard practice. Particulate contamination is removed from the system by circulating pre-cleaned hydraulic fluid or solvent through the lines. This flushing of the particulates is typically carried out utilizing air over hydraulic pumps, diesel engine driven triplex pumps, and electric motor driven triplex pumps. The cleanliness of the fluid is quantified according to a specification called NASA 1638, which was developed by NASA for the space program. After flushing, the hydraulic system is pressure tested for leakage.
The hydraulic control lines in such systems are typically several thousand feet long and of small diameter. The control lines are engineered so as to provide reliable operation of the control devices, rather than to facilitate cleaning. High flow rate is not required to actuate the control devices on the seabed floor, but turbulent flow through the lines is essential to efficiently sweep the particulates to the surface for capture. High pressure is required to cause turbulent flow, but it cannot be too high, or the pressure capabilities of the hydraulic system may be exceeded, causing damage to the components.
One prior art solution to this problem was to limit the output pressure of the cleaning fluid pump by diverting a portion of the fluid through a bypass valve set to open at a pre pressure. Normal operation in this prior art solution was to operate with the bypass valve open. This procedure has several draw-backs. One is that the diverted cleaning fluid will heat up, which will necessitate utilization of a bigger cooler. The resulting system will be less compact and heavier than a system without a cleaning fluid cooler, or a system with a small cooler, which is a drawback for use on offshore oil platforms. The system will also be more expensive to build and operate. Another is that a larger pump motor will be required, as a portion of its work will be wasted in heating the cleaning fluid. This adds weight to the unit, expense to its construction, and higher operating costs. A further drawback is that motor life will be shortened due to its continuous operation.
Another prior art solution was to couple the pump to a pressure switch and turn the pump off and on between high and low pressure limits. This procedure is incapable of maintaining optimal flow of cleaning fluid through the lines.
These problems are worsened where the conditions of application require low flow at high pressures to clean the system.
An apparatus which overcomes these shortcomings would be very desirable.
It is an object of this invention to provide a method to obtain optimized turbulent flow in a hydraulic cleaning system without bypassing fluid, which can introduce excessive heat to the fluid and degrade it.
It is a further object of this invention to provide a method for dissipating heat that may come from long periods of turbulent flow through a hydraulic system in the process of being cleaned.
It is a further object of this invention to provide a hydraulic cleaning system which has the further capability of supplying increased static pressure for hydrostatic pressure test on hydraulic components and is adaptable to act as a hydraulic pressure control system to operate valve and other hydraulic equipment that has been flushed and pressure tested by the unit.
It is a further object of this invention to unitized assembly for cleaning hydraulic systems that is easily portable and which can be transported via trailer, work boat, helicopter, or other conveyance.
It is an additional object of this invention to provide a hydraulic cleaning unit that does not require transport of flammable fuels to operate it and which can be easily made explosion proof and intrinsically safe to operate in a class I Div II hazardous area without igniting a gaseous atmosphere.
It is an additional object to provide a unit that does not emit any hazardous emissions and can be operated in an enclosed area safely as well as to provide a unit which runs quietly and does not add to poise pollution.
It is an additional object of this invention to provide a packaged cleaning system that is adaptable for providing information for flow rate, total fluid consumption, pressure, and temperature of the fluid. It can also provide over pressure protection and hours of operation. This unit is easily interfaced for computer date logging technology.
It is yet another object of the invention to provide a unit capable of taking a sample of fluid on the fly while the unit is flushing so it can be analyzed while flushing continues. The unit is adaptable so it may continue to flush while samples of fluid are automatically analyzed with the results may be logged to a computer and to perform an automatic shutdown when the system is to be clean.
In one embodiment, the invention provides a multi-purpose injector unit for injecting liquid into a hydraulic control system. The unit comprises a filtration system, a primary pump, an accumulator, a first manifold, a second manifold, and a flow path means.
The filtration system is for receiving a contaminated liquid and forming a filtered liquid. The primary pump is in flow communication with the filtration system and receives filtered liquid from the filtration system. The accumulator is in flow communication with the pump and receives filtered liquid from the pump and stores the filtered liquid at an elevated pressure. The first manifold is in flow communication with the accumulator and receives filtered liquid from the accumulator and distributes filtered liquid into the hydraulic control system. The second manifold is positioned to receive contaminated liquid from the hydraulic control system. The flow path means forms a flow path between the second manifold and the filtration system to provide for the filtering of the contaminated liquid in the filtration system.
In another embodiment of the invention, there is provided a method for internally cleaning a hydraulic control system. The method is carried out by establishing a turbulent flow of cleaning fluid through the hydraulic control system, and maintaining the turbulent flow until the hydraulic control system has been cleaned without diverting a portion of cleaning fluid through a bypass valve, by use of a variable speed pump coupled to a fluid accumulator.